Magnetic particle inspection probe with adjustable probe legs and self-contained circuitry for a.c. or d.c. testing



Aprxl 16, 1968 P. J. PARKER 3,378,762

1 MAGNETIC PARTICLE INSPECTION PROBE WITH ADJUSTABLE PROBE LEGS ANDSELF-CONTAINED CIRCUITRY FOR A.C. OR D.C. TESTING Original Filed Sept.2, 1964 2 Sheets-Sheet 1 ,2 7o '9 i f P l l I2 i. O

I 1 l I it l 56 INVENTOR.

PHILLIP J. PARKER ATTORNEY Aprll 16, 1968 p, J, PARKER 3,378,762

MAGNETIC PARTICLE INSPECTION PROBE WITH ADJUSTABLE PROBE LEGS ANDSELF-CONTAINED CIRCUITRY FOR A.C. OR D.C. TESTING Original Filed Sept.2. 1964 2 Sheets-Sheet 1 e2 J L INVENTOR.

PHILLIP J. PARKER ATTORNEY United States Patent 3,378,762 MAGNETICPARTICLE INSPECTION PROBE WITH ADJUSTABLE PROBE LEGS AND SELF-CON-TAINED CIRCUITRY FOR A.C. 0R D.C. TESTING Phillip J. Parker, 1714 SantaAnna Drive, Dunedin, Fla. 33528 Continuation of application Ser. No.394,028, Sept. 2, 1964. This application July 5, 1967, Ser. No. 651,3218 Claims. (Cl. 324-38) This is a continuation of application Ser. No.394,028, filed Sept. 2, 1964. i

The present invention relates to a contour probe, or device forrevealing surface or near subsurface defects such as cracks or foreignsubstances in magnetizable ferrous objects or materials. Such cracks ordefects are often not detectible by visual inspection, and musttherefore be discovered by other means of greater effectiveness.

One means of detection, or inspection, comprises creating a magneticfield in the ferrous object to be tested, and applying to the magnetizedarea a quantity of minute metal particles such as fine iron filings. Ifa defect is present in the magnetized area, the locale of the defectwill so attract the metal particles as to outline the defect. Thismethod is known as the magnetic particle inspection method ofnon-destructive testing.

An object of the present invention is to improve the technique oftesting by the magnetic particle inspection method, and to improve theapparatus used in performing the method.

Another object of the invention is to enlarge the scope of testing bymeans of an electro-mechanical probe of improved construction.

A further object is to provide an improved probe for detecting defectswith the use of alternatively selectible means built into the probe,whereby to enhance the effectiveness and the scope of use under varioustest conditions.

Another object is to provide a testing probe of the character stated,which lends itself to detecting flaws or defects in objects which may bequite irregular of contour, or characterized by offsets, corners,curvatures, and other departures from a relatively simple planarformation.

The foregoing and other objects are attained by the means describedherein and illustrated upon the accompanying drawings, in which:

FIG. 1 is a side elevational view of the improved contour probeemploying the present invention.

FIG. 2 is an end elevation of the same.

FIG. 3 is a top plan View of the same.

FIG. 4 is a perspective view showing a defective ferrous articleundergoing testing for flaws.

FIG. 5 is a side elevation of the contour probe, in one position ofadjustment.

FIG. 6 is a similar view showing a seocnd adjusted position.

FIG. 7 is a similar view showing a third adjusted position.

FIG. 8 is a similar view showing the probe in condition for testing acylinder for defects.

FIG. 9 is a schematic wiring diagram illustrating one arrangement ofelectrical components that may be built into the probe.

In general, the contour probe may comprise a hollow elongate non-ferroushousing 10 having an inverted U- shaped forward end 12 and an invertedU-shaped rear end 14, connected by means of a handle 16. The ends 12 and14 may be apertured transversely to receive bolts 18 and 20,respectively, from which may depend the jointed legs 22 and 24. The legsare constructed of magnetic material, such as electrical steellaminations, as will be explained.

Intermediate the forward and rear ends 12 and 14 of the housing, andbeneath handle 16, is supported an electrical magnetizing coil 26. Thecoil surrounds an elongate core 28 of magnetizable steel laminations,the core having opposite ends 30 and 32 which are perforated toaccommodate the bolts 18 and 20. Bolts 18 and 20 accordingly may beutilized to fix core 28 to housing 10 while the core supports coil 26,and to suspend the jointed legs 22 and 24 from the housing. Uponloosening the nuts of bolts 18 and 20, the jointed legs may be swung tovarious testing positions, for example as illustrated by FIGS. 5 through8.

Each core lamination may be in the form of a thin ferrous metal striphaving one end rounded off and perforated to receive a bolt such as 18,whereas the opporsite end of the strip terminates in a foreshortenedbias-cut end 34. A multiplicity of such strips, arranged in end-to-endalternation, makes up the composite core having perforated opposite endsto receive the bolts 18 and 20.

Leg 24 may comprise an upper section 36 and a lower section 38,pivotally connected by means of a bolt 40 to permit angular dispositionof the sections as exemplified by FIGS. 5 through 8. Upper section 36comprises a multiplicity of thin ferrous metal strips like those of core28 just described, but shorter in length. Each strip or lamination ofsection 36 may have a rounded end 42 perforated to receive a bolt, forexample bolt 40, and an opposite end terminating as a foreshortenedbias-cut end 44. A multiplicity of such strips, arranged in end-to-endalternation, makes up the composite section 36 having perforatedopposite ends to receive the bolts 40 and 20. Alternate strips ofsection 36 fit between alternate strips of core 28, to eifect a firmpivotal connection at bolt 20, FIG. 2.

The lower section 38 of leg 24 may be constructed in a manner quitesimilar to section 36, and as above described, with the exception thatthe thin metal laminations of section 38 all terminate in a planeforming a free end 46 of leg section 38. The laminations of bothsections may be suitably secured as by means of rivets or otherfasteners 48 and 50, to unify the components of the sections.

Leg 22 is constructed as above explained, so that the legs 24 and 22 aresimilar. It will accordingly be understood that by loosening the nuts ofbolts 18, 20, 40, 40, the several leg sections may be disposed invarious relative positions, some of which are depicted by FIGS. 5through 8. The sections may be locked in such positions, when desired,by tightening the nuts of bolts 18, 20, 40, 40.

By energizing the coil 26 with either an alternating electric current(A.C.), or a pulsating direct current (D. C.), the free ends of legs 22and 24 become magnetized and will create a magnetic field as indicatedupon FIG. 4, within a ferrous metal plate or object 52 to be tested,

If the plate or object 52 contains cracks or other defects 54 within thearea of the magnetic field, a sprinkling of ferrous metal particles orfine iron filings applied to the area will be attracted to the defects,and thereby clearly outline them. Movement of the particles toward thedefects is of course expedited by vibrations imposed upon object 52 bythe alternating or pulsing characterof the current used in energizingcoil 26.

In the several drawing views, the reference numeral 56 indicates a powercord whereby electric current is supplied for operating the contourprobe. Power may be supplied from a standard 115 volt A.C. 6O cyclesource, which may be utilized as such, or which may be converted to apulsating direct current capable of being varied by the operator of theprobe for obtaining certain test advantages, as Will be explained.

It may here be noted that the adjustable jointed legs 22 and 24 enablethe probe to conform to various irregular or odd-shaped surfaces of anobject to be tested, and

may be so adjusted as to perform tests upon contoured surfaces such asthe inside or outside of a cylinder, around corners and offsets, and thelike. Moreover, the span of the legs may be increased or decreased toobtain the most effective test possible under various conditions, and ifdesired, the legs may be locked at bolts 18, 20, 40, 40, for theperformance of repeat tests on a series of identical parts or objects tobe tested.

In its most desirable form, the probe of the invention may be providedwith means for energizing coil 26 selectively, with A.C. (alternatingcurrent), or DC. (direct current), the latter being variable to producean exceptionally strong or an exceptionally weak magnetic field fortesting. It is found that a strong A.C. field is desirable for certaintypes of inspection, or to demagnetize work which had retained unwantedresidual magnetism. On the other hand, the pulsating D.C.type currentmay be more effectively employed where test objects may vary in size andmass, so that current of greater or lesser intensity, or leg spans ofdifferent amounts, may best be employed to obtain maximum test results.It is therefore desirable to build into housing 10, a compactlightweight means for selecting and varying the type and intensity ofcurrent which may be needed for effectively testing or inspectingwork-pieces or objects having widely different characteristics.

To use A.C. power, the magnetizing coil 26 may be simply connectedacross the 115 volt conductors 6t) and 62 (FIG. 9) by means of a manualswitch 64 mounted upon the housing. In the simplest form of the probe,core 26 may be so energized without resort to additional circuitry. Theline voltage may vary from zero to 125 volts A.C. without damage to thecoil, as long as the cycle frequency is about 50 cycles or higher. Ifthe applied voltage be decreased, the magnetic field of coil 26 will becorrespondingly reduced.

The current in the coil is limited principally by the inductance of thecoil, resistance being deliberately reduced to a low value to avoidexcessive heating of the coil. In use, the inductance will vary over awide range as objects of different sizes are placed across the legs orpole pieces 22, 24, and removed therefrom. This condition will alsocause the current to vary as the current is limited by the free airinductance to a fairly low value to prevent an operating condition whichmight damage the coil through overheating. In actual operation, currentis further reduced by the presence of the iron core 28.

By flipping switch 64 to engage the contact 66, the A.C. supply may beterminated, and replaced by pulsating DC. power to energize coil 26. TheDC. supply, by preference, avoids use of a transformer in order that allof the necessary circuitry might be built within housing 10, therebyeliminating the need for a heavy carrying case or separate power unit.

The foregoing advantage, amongst others, may be achieved byincorporating a silicon controlled rectifier SCR as a means ofrectifying the A.C. to D.C., and utilizing the same rectifier in aswitching function. The switching reduces the average current byallowing conduction for only a short period of each half cycle of thepower frequency. A characteristic of the silicon controlled rectifier isthat it will conduct only in one direction, and will conduct only afterreceiving a gate signal. When conduction has started, it acts somewhatas a switch and at the same time performs the rectifier function.However, the current through SCR must be limited by the external load,which is the coil 26.

Removal of the gate signal does not alter the SCR conducting; it is onlyafter the current has dropped to a very low level and remains there fora short interval, that the conduction is shut off. The shut-off timeinterval is much shorter than the power frequency.

The gate pulse is provided by a unijunction transistor U, which hasbreak-down characteristics that permit voltage to build up in condenserC to a critical potential when it begins to conduct heavily. Theresulting current pulse is in turn passed to the gate input of thesilicon controlled rectifier. Then, the unijunction conduction ceases asthe current has decreased to a low value, and again the build-up beginsin condenser C.

The rate of C/unijunction build up may be controlled by a potentiometerP, the control range being fixed by a limit resistor R2. The voltagesource for charging condenser C is from the rectifier and voltagedivider CR1, R4, and R5.

In operation, the time required to fire the unijunction U is always amuch shorter interval than one cycle. Under a maximum output, rectifierSCR is never in conduction for more than one-third of the cycle to aminimum of a very small portion of one cycle which is selected from theright side or declining slope of the cycle. Limit resistor R2 isselected to prevent the rectifier SCR from being fired for more thanone-third of the cycle. The value of potentiometer resistor R1 and otherresistors to some extent may be varied for achieving maximum delay offiring.

The accumulated tolerance build-up of all affected components andresulting variations are designed to permit potentiometer P to functionfrom an off condition, or almost nil, to the full rating achieved at themaximum of one-third of one cycle. Condenser C2 and resistor R6 functionto suppress radio frequency interference.

As a possible modification of the circuitry, there is shown at SD bymeans of broken lines, a silicon diode connected between the anode ofsilicon controlled rectifier SCR, and one side of coil 26, thereby toshunt the coil. Incorporation of the silicon diode is found to have adesirable stabilizing influence upon the DC. pulsations. In the typicalcircuit of FIG. 9, the various components may have values as follows:

R125K1 w. pot. log 40% taper R24700' /1 w. 5% resistor R3-1200 /2 w. 5%resistor R415K /2 w. 5% resistor R5120 /2 w. 5% resistor R627 /2 w. 5%resistor C.5 mfd. V. DC. w. cap. C2-.01 mfd. 1600 v. disc. cap.

U2N 1671A unijunction SCRSilicon controlled rectifier CRl-SOO ma.400P.I.V. silicon rectifier Switch 64 may be a single-pole double-throwswitch of conventional type. Switch 70, if furnished, may be asingle-pole single-throw push-button switch of conventional type. Thevalues and types of components listed above may be varied within theskill of the electronics expert, without materially altering ordepreciating the functions thereof, within acceptable limits.

In conclusion, it may be pointed out that the contour probe hereindisclosed may find valuable application throughout the metal-workingindustry, to inspect raw materials, work in process, finished work, andthe like. Application would include also the inspection of welds,ferrous castings, and parts requiring periodic checking while inservice, examples of which may include cylinder blocks and heads,crank-shafts, and other vital machine components which might be expectedto fail under continued or repeated working stress. In fact, the scopeof application is almost without limit.

Another important use of the contour probe is in the field ofnon-destructive laboratory testing, to determine high level evaluationof critical defects, and to establish testing standards.

It is to be understood that various modifications and changes may bemade in the device, within the scope of the appended claims, withoutdeparting from the spirit of the invention. Such modifications mayinclude eliminating the direct-current circuitry in the interest ofeconomy, but with an accompanying loss of service range; or, providing asubstitute generator of direct current pulsation employing a transformerand current intensity controls, which have the obvious disadvantages ofexcessive weight and bulk such as to render impractical or impossiblecontainment within the limits of the prob housing. Various othermodifications and changes within the scope of the appended claims, maybecome manifest to persons skilled in the art to which the inventionappertains.

I claim:

1. A portable magnetic device for revealing by magnetic particleorientation defects in ferrous objects, and comprising in combination:an elongate hollow nonferro-us housing including a handle, and having aforward end and a rear end spaced apart; a hollow electrical magnetizingcoil intermediate said spaced ends; an elongate magnetizable coresupported by the housing and passing lengthwise through the hollow coil,said core having opposite ends disposed exteriorly of the coil; a pairof elongate magnetizable probe legs each having a free end and amounting end; said legs each comprising an upper section, a lowersection, and means pivoting the lower section to the upper sectionwhereby said pivoted sections may be disposed angularly to one another;means adjacent to each end of the magnetizable core for pivotallysupporting the mounting end of each probe leg; a first electric circuitwithin the housing for delivering alternating electric current to thesaid magnetizable coil; a second electric circuit within the housingincluding means therein for converting alternating electric current to apulsating direct current and delivering pulsating direct current to saidmagnetizable coil, and electrical switch means on the housing handleconnected in said circuits, for alternatively connecting the first andsecond electric circuits to a common source of alternating current forproviding said magnetizing coil and its associated probe legs with analternating magnetizing current from the first circuit, or with apulsating direct magnetizing current from said second circuit.

2. The device as set forth in claim 1, wherein the combination includesadjustable rheostat in the second magnetizing circuit for varying andcontrolling the intensity of the pulsating direct current generated bysaid second circuit.

3. The combination set forth in claim 1, wherein the magnetizable corecomprising a multiplicity of uniformly thin ferrous metal strips inflatwise contact, with alternate strips perforated and extendedlongitudinally to provide spaces thcrebetween; the upper sections ofsaid probe legs comprising a multiplicity of uniformly thin ferrousmetal strips in flatwise contact, with alternate strips thereofperforated and extended longitudinally to provide spaces therebetween atopposite ends of said sections, the perforated extensions of the corestrips being received in the spaces between the perforated extensions atone end of the upper leg section strips, with the perforations thereofin registry; means extending through the registered perforations forpivotally securing the upper leg sections to opposite ends of the core;and the lower sections of said legs each comprising a multiplicity ofuniformly thin ferrous strips in flatwise contact, with alternate stripsthereof perforated and extended longitudinally at one end of each lowersection to provide spaces therebetween receptive of the remainingperforated extensions of the upper leg section; and means extendingthrough the perforations of the lower leg section extensions and theregistered perforations of the extensions of said remaining perforatedextensions of the upper leg section, for pivotally securing the lowersections to the upper sections of said probe legs.

4. A magnetic device for revealing by magnetic particle orientationdefects in ferrous objects, and comprising in combination: an elongatehollow non-ferrous housing having a forward end and a rear end spacedapart; a hollow electrical magnetizing coil intermediate said spacedends; a laminated, elongate magnetizable core supported by the housingand passing through the hollow coil, said core having opposite endsdisposed exteriorly of the coil; a pair of laminated, elongatemagnetizable probe legs each having a free end and a mounting end; meanspivotally supporting the mounting end of each probe leg to an end of themagnetizable core; a first electric magnetizing circuit within thehousing for delivering alternat ing electric current to said coil; asecond electric magnetizing circuit within the housing including meanstherein for converting alternating electric current to a pulsatingdirect current and delivering pulsating direct current to said coil, andelectrical switch means connected in said magnetizing circuits forselectively connecting one or the other of said circuits to a commonsource of alternating current for providing either alternating currentmagnetization or pulsating direct current magnetization to said probelegs.

5. The combination set forth in claim 4 including a manually operable,normally-open electrical switch in series circuit with each of the saidmagnetizing circuits and a common source of alternating current.

6. A portable magnetic device for revealing by magnetic particleorientation defects in ferrous objects, and comprising in combination:an elongate hollow non-ferrous housing including a handle, and having aforward end and rear end spaced apart; a hollow electrical magnetizingcoil intermediate said spaced ends; an elongate magnetizable coresupported by the housing and passing lengthwise through the hollow coil,said core having opposite ends disposed exteriorly of the coil; a pairof elongate magnetizable prob legs each having a free end and a mountingend; said legs each comprising an upper section, a lower section, andmeans pivoting the lower section to the upper section whereby saidpivoted sections may be disposed angularly to one another; mean adjacentto each end of the magnetizable core for pivotally supporting themounting end of each probe leg; a first electric circuit within thehousing for delivering alternating electric current to the saidmagnetizable coil; a second electric circuit within the housingincluding rectifier means for converting alternating electric current toa pulsating direct current and delivering pulsating direct current tosaid magnetizable coil, said second electric circuit including phasecontrol switching means for turning the rectifier means on for not morethan about /3 of a cycle selected from the declining slope of the cycleto obtain sharp pulses, and electrical switch means on the housinghandle connected in said circuits, for alternatively connecting thefirst and second electric circuits to a common source of alternatingcurrent for providing said magnetizing coil and its associated probelegs with an alternating magnetizing current from the first circuit, orwith a pulsating direct magnetizing current from said second circuit.

7. The device as set forth in claim 6, wherein the combination includesadjustable rheostat in the second mag- 7 netizing circuit for varyingand controlling the intensity of the pulsating direct current generatedby said second circuit.

8. Th combination set forth in claim 6, wherein the magnetizable corecomprising a multiplicity of uniformly thin ferrous metal strips in flatWise contact, with alternate strips perforated and extendedlongitudinally to provide spaces therebetween; the upper sections ofsaid probe legs comprising a multiplicity of uniformly thin ferrousmetal strips in flatwise contact, with alternate strips thereofperforated and extended longitudinally to provide spaces therebetween atopposite ends of said sections, the perforated extensions of the corestrips being received in the spaces between the perforated extensions atone end of the upper leg section strips, with the perforations thereofin registry; means extending through the registered perforations forpivotally securing the upper leg sections to opposite ends of th core;and the lower sections of said legs each comprising a multiplicity ofuniformly thin ferrous strips in flatwise contact, with alternate stripsthereof perforated and extended longitudinally at one end of each lowersection to provide spaces therebetween rece tive of the remainingperforated extensions of the upper leg section; and means extendingthrough the perforations of the lower leg section extensions and theregistered perforations of the extensions of said remaining perforatedextensions of the upper leg section, for pivotally securing the lowersections to the upper sections of said probe legs.

References Cited UNITED STATES PATENTS OTHER REFERENCES McMasters,Robert C.: Non-Destructive Testing Handbook, vol. II, p. 308, The RonaldPress Co., New York, N.Y., 1963.

RUDOLPH V. ROLINEC, Primary Examiner.

R. I. CORCORAN, Assistant Examiner.

1. A PORTABLE MAGNETIC DEVICE FOR REVEALING BY MAGNETIC PARTICLEORIENTATION DEFECTS IN FERROUS OBJECTS, AND COMPRISING IN COMBINATION:AN ELONGATE HOLLOW NONFERROUS HOUSING INCLUDING A HANDLE, AND HAVING AFORWARD END AND A REAR END SPACED APART; A HOLLOW ELECTRICAL MAGNETIZINGCOIL INTERMEDIATE SAID SPACED ENDS; AN ELONGATE MAGNETIZABLE CORESUPPORTED BY THE HOUSING AND PASSING LENGTHWISE THROUGH THE HOLLOW COIL,SAID CORE HAVING OPPOSITE ENDS DISPOSED EXTERIORLY OF THE COIL; A PAIROF ELONGATE MAGNETIZABLE PROBE LEGS EACH HAVING A FREE END AND AMOUNTING END; SAID LEGS EACH COMPRISING AN UPPER SECTION, A LOWERSECTION, AND MEANS PIVOTING THE LOWER SECTION TO THE UPPER SECTIONWHEREBY SAID PIVOTED SECTIONS MAY BE DISPOSED ANGULARLY TO ONE ANOTHER;MEANS ADJACENT TO EACH END OF THE MAGNETIZABLE CORE FOR PIVOTALLYSUPPORTING THE MOUNTING END OF EACH PROBE LEG; A FIRST ELECTRIC CIRCUITWITHIN THE HOUSING FOR DELIVERING ALTERNATING ELECTRIC CURRENT TO THESAID MAGNETIZABLE COIL; A SECOND ELECTRIC CIRCUIT WITHIN THE HOUSINGINCLUDING MEANS THEREIN FOR CONVERTING ALTERNATING ELECTRIC CURRENT TO APULSATING DIRECT CURRENT AND DELIVERING PULSATING DIRECT CURRENT TO SAIDMAGNETIZABLE COIL, AND ELECTRICAL SWITCH MEANS ON THE HOUSING HANDLECONNECTED IN SAID CIRCUITS, FOR ALTERNATIVELY CONNECTING THE FIRST ANDSECOND ELECTRIC CIRCUITS TO A COMMON SOURCE OF ALTERNATING CURRENT FORPROVIDING SAID MAGNETIZING COIL AND ITS ASSOCIATED PROBE LEGS WITH ANALTERNATING MAGNETIZING CURRENT FROM THE FIRST CIRCUIT, OR WITH APULSATING DIRECT MAGNETIZING CURRENT FROM SAID SECOND CIRCUIT.